On Fri, 15 Jul 2016 10:54:38 +0100, piglet <erichpwagner@hotmail.com> wrote:>On 14/07/2016 21:51, bitrex wrote: >> On 07/14/2016 04:27 PM, John Larkin wrote: >>> >>> Seven cold filaments could pull a lot of current. You could do >>> software tricks to soften the turn-ons, but the display might look >>> silly. >>> >>> >> >> I'm going to give preheating the filaments via PWMing the "shutdown" pin >> of the boost module a try, though I'll have to check the datasheet to >> see what the delay from a high level applied to that pin to output power >> good is. >> >> If that's not plausible I can try PWMing the "ripple blanking" input to >> the '47. > >Could be easier just to add resistors across LS47 outputs to preheat, >depending on ease of changing hardware vs software I suppose. > >pigletRemember the old T-bird sequential turn signals? Original Ford design was a motor driving a cam-shaft that operated switches that sequenced the tail lights. I converted it to a chip driving power transistors, but power transistors couldn't cope with the 10X current surge, without pre-warm, which was complex and power wasting. Ultimately used SCR's. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
Driving 74LS from 3.3V uP
Started by ●July 12, 2016
Reply by ●July 15, 20162016-07-15
Reply by ●July 15, 20162016-07-15
On Fri, 15 Jul 2016 09:56:19 -0400, bitrex <bitrex@de.lete.earthlink.net> wrote:>On 07/15/2016 05:54 AM, piglet wrote: >> On 14/07/2016 21:51, bitrex wrote: >>> On 07/14/2016 04:27 PM, John Larkin wrote: >>>> >>>> Seven cold filaments could pull a lot of current. You could do >>>> software tricks to soften the turn-ons, but the display might look >>>> silly. >>>> >>>> >>> >>> I'm going to give preheating the filaments via PWMing the "shutdown" pin >>> of the boost module a try, though I'll have to check the datasheet to >>> see what the delay from a high level applied to that pin to output power >>> good is. >>> >>> If that's not plausible I can try PWMing the "ripple blanking" input to >>> the '47. >> >> Could be easier just to add resistors across LS47 outputs to preheat, >> depending on ease of changing hardware vs software I suppose. >> >> piglet >> > >I'm hoping to get a few PCBs of the circuit I'm working on made if it >turns out alright, so I'd like to keep everything as compact as possible >and do it in software if I can, rather than add a resistor network to >the board. > >In the final design I'd like to ditch the LS chip entirely and simply >use a uP of the same architecture with enough pins to handle all the >segments directly. Many AVR chips are rated to sink 200mA to ground >total through all pins, which surprised me a bit...though this circuit >would push that limit and perhaps make me feel a little uncomfortable. > >I'd also like to dynamically adjust the voltage to the segments >depending on how many are lit to increase battery life via PWM, but that >may not be possible if the boost's enable pin can't handle being PWMed, >so I may have to use a driver of some type. The cost/space advantage of >using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not >gigantic.Well, you could fast-forward 40 years or so and use LED displays. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●July 15, 20162016-07-15
On Fri, 15 Jul 2016 09:56:19 -0400, bitrex wrote:> On 07/15/2016 05:54 AM, piglet wrote: >> On 14/07/2016 21:51, bitrex wrote: >>> On 07/14/2016 04:27 PM, John Larkin wrote: >>>> >>>> Seven cold filaments could pull a lot of current. You could do >>>> software tricks to soften the turn-ons, but the display might look >>>> silly. >>>> >>>> >>>> >>> I'm going to give preheating the filaments via PWMing the "shutdown" >>> pin of the boost module a try, though I'll have to check the datasheet >>> to see what the delay from a high level applied to that pin to output >>> power good is. >>> >>> If that's not plausible I can try PWMing the "ripple blanking" input >>> to the '47. >> >> Could be easier just to add resistors across LS47 outputs to preheat, >> depending on ease of changing hardware vs software I suppose. >> >> piglet >> >> > I'm hoping to get a few PCBs of the circuit I'm working on made if it > turns out alright, so I'd like to keep everything as compact as possible > and do it in software if I can, rather than add a resistor network to > the board. > > In the final design I'd like to ditch the LS chip entirely and simply > use a uP of the same architecture with enough pins to handle all the > segments directly. Many AVR chips are rated to sink 200mA to ground > total through all pins, which surprised me a bit...though this circuit > would push that limit and perhaps make me feel a little uncomfortable. > > I'd also like to dynamically adjust the voltage to the segments > depending on how many are lit to increase battery life via PWM, but that > may not be possible if the boost's enable pin can't handle being PWMed, > so I may have to use a driver of some type. The cost/space advantage of > using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not > gigantic.Why not just use transistor arrays? -- Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com
Reply by ●July 15, 20162016-07-15
On Fri, 15 Jul 2016 10:50:21 -0500, Tim Wescott <tim@seemywebsite.com> wrote:>On Fri, 15 Jul 2016 09:56:19 -0400, bitrex wrote: > >> On 07/15/2016 05:54 AM, piglet wrote: >>> On 14/07/2016 21:51, bitrex wrote: >>>> On 07/14/2016 04:27 PM, John Larkin wrote: >>>>> >>>>> Seven cold filaments could pull a lot of current. You could do >>>>> software tricks to soften the turn-ons, but the display might look >>>>> silly. >>>>> >>>>> >>>>> >>>> I'm going to give preheating the filaments via PWMing the "shutdown" >>>> pin of the boost module a try, though I'll have to check the datasheet >>>> to see what the delay from a high level applied to that pin to output >>>> power good is. >>>> >>>> If that's not plausible I can try PWMing the "ripple blanking" input >>>> to the '47. >>> >>> Could be easier just to add resistors across LS47 outputs to preheat, >>> depending on ease of changing hardware vs software I suppose. >>> >>> piglet >>> >>> >> I'm hoping to get a few PCBs of the circuit I'm working on made if it >> turns out alright, so I'd like to keep everything as compact as possible >> and do it in software if I can, rather than add a resistor network to >> the board. >> >> In the final design I'd like to ditch the LS chip entirely and simply >> use a uP of the same architecture with enough pins to handle all the >> segments directly. Many AVR chips are rated to sink 200mA to ground >> total through all pins, which surprised me a bit...though this circuit >> would push that limit and perhaps make me feel a little uncomfortable. >> >> I'd also like to dynamically adjust the voltage to the segments >> depending on how many are lit to increase battery life via PWM, but that >> may not be possible if the boost's enable pin can't handle being PWMed, >> so I may have to use a driver of some type. The cost/space advantage of >> using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not >> gigantic. > >Why not just use transistor arrays?I suspect the OP's problem is collapsing the "eBay special"... persistently ignoring the fact that filament-type bulbs have ~10X current when cold. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
Reply by ●July 15, 20162016-07-15
On 07/15/2016 11:35 AM, John Larkin wrote:> On Fri, 15 Jul 2016 09:56:19 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 07/15/2016 05:54 AM, piglet wrote: >>> On 14/07/2016 21:51, bitrex wrote: >>>> On 07/14/2016 04:27 PM, John Larkin wrote: >>>>> >>>>> Seven cold filaments could pull a lot of current. You could do >>>>> software tricks to soften the turn-ons, but the display might look >>>>> silly. >>>>> >>>>> >>>> >>>> I'm going to give preheating the filaments via PWMing the "shutdown" pin >>>> of the boost module a try, though I'll have to check the datasheet to >>>> see what the delay from a high level applied to that pin to output power >>>> good is. >>>> >>>> If that's not plausible I can try PWMing the "ripple blanking" input to >>>> the '47. >>> >>> Could be easier just to add resistors across LS47 outputs to preheat, >>> depending on ease of changing hardware vs software I suppose. >>> >>> piglet >>> >> >> I'm hoping to get a few PCBs of the circuit I'm working on made if it >> turns out alright, so I'd like to keep everything as compact as possible >> and do it in software if I can, rather than add a resistor network to >> the board. >> >> In the final design I'd like to ditch the LS chip entirely and simply >> use a uP of the same architecture with enough pins to handle all the >> segments directly. Many AVR chips are rated to sink 200mA to ground >> total through all pins, which surprised me a bit...though this circuit >> would push that limit and perhaps make me feel a little uncomfortable. >> >> I'd also like to dynamically adjust the voltage to the segments >> depending on how many are lit to increase battery life via PWM, but that >> may not be possible if the boost's enable pin can't handle being PWMed, >> so I may have to use a driver of some type. The cost/space advantage of >> using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not >> gigantic. > > Well, you could fast-forward 40 years or so and use LED displays. >Doesn't look as cool at Burning Man, no fun at all.
Reply by ●July 15, 20162016-07-15
On 07/15/2016 12:30 PM, Jim Thompson wrote:> On Fri, 15 Jul 2016 10:50:21 -0500, Tim Wescott <tim@seemywebsite.com> > wrote: > >> On Fri, 15 Jul 2016 09:56:19 -0400, bitrex wrote: >> >>> On 07/15/2016 05:54 AM, piglet wrote: >>>> On 14/07/2016 21:51, bitrex wrote: >>>>> On 07/14/2016 04:27 PM, John Larkin wrote: >>>>>> >>>>>> Seven cold filaments could pull a lot of current. You could do >>>>>> software tricks to soften the turn-ons, but the display might look >>>>>> silly. >>>>>> >>>>>> >>>>>> >>>>> I'm going to give preheating the filaments via PWMing the "shutdown" >>>>> pin of the boost module a try, though I'll have to check the datasheet >>>>> to see what the delay from a high level applied to that pin to output >>>>> power good is. >>>>> >>>>> If that's not plausible I can try PWMing the "ripple blanking" input >>>>> to the '47. >>>> >>>> Could be easier just to add resistors across LS47 outputs to preheat, >>>> depending on ease of changing hardware vs software I suppose. >>>> >>>> piglet >>>> >>>> >>> I'm hoping to get a few PCBs of the circuit I'm working on made if it >>> turns out alright, so I'd like to keep everything as compact as possible >>> and do it in software if I can, rather than add a resistor network to >>> the board. >>> >>> In the final design I'd like to ditch the LS chip entirely and simply >>> use a uP of the same architecture with enough pins to handle all the >>> segments directly. Many AVR chips are rated to sink 200mA to ground >>> total through all pins, which surprised me a bit...though this circuit >>> would push that limit and perhaps make me feel a little uncomfortable. >>> >>> I'd also like to dynamically adjust the voltage to the segments >>> depending on how many are lit to increase battery life via PWM, but that >>> may not be possible if the boost's enable pin can't handle being PWMed, >>> so I may have to use a driver of some type. The cost/space advantage of >>> using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not >>> gigantic. >> >> Why not just use transistor arrays? > > I suspect the OP's problem is collapsing the "eBay special"... > persistently ignoring the fact that filament-type bulbs have ~10X > current when cold. > > ...Jim Thompson >Hey! I recognized that fact this time yesterday.
Reply by ●July 15, 20162016-07-15
On Friday, 15 July 2016 17:30:43 UTC+1, Jim Thompson wrote:> On Fri, 15 Jul 2016 10:50:21 -0500, Tim Wescott <tim@seemywebsite.com> > wrote: > >On Fri, 15 Jul 2016 09:56:19 -0400, bitrex wrote: > >> On 07/15/2016 05:54 AM, piglet wrote: > >>> On 14/07/2016 21:51, bitrex wrote: > >>>> On 07/14/2016 04:27 PM, John Larkin wrote: > >>>>> > >>>>> Seven cold filaments could pull a lot of current. You could do > >>>>> software tricks to soften the turn-ons, but the display might look > >>>>> silly. > >>>>> > >>>>> > >>>>> > >>>> I'm going to give preheating the filaments via PWMing the "shutdown" > >>>> pin of the boost module a try, though I'll have to check the datasheet > >>>> to see what the delay from a high level applied to that pin to output > >>>> power good is. > >>>> > >>>> If that's not plausible I can try PWMing the "ripple blanking" input > >>>> to the '47. > >>> > >>> Could be easier just to add resistors across LS47 outputs to preheat, > >>> depending on ease of changing hardware vs software I suppose. > >>> > >>> piglet > >>> > >>> > >> I'm hoping to get a few PCBs of the circuit I'm working on made if it > >> turns out alright, so I'd like to keep everything as compact as possible > >> and do it in software if I can, rather than add a resistor network to > >> the board. > >> > >> In the final design I'd like to ditch the LS chip entirely and simply > >> use a uP of the same architecture with enough pins to handle all the > >> segments directly. Many AVR chips are rated to sink 200mA to ground > >> total through all pins, which surprised me a bit...though this circuit > >> would push that limit and perhaps make me feel a little uncomfortable. > >> > >> I'd also like to dynamically adjust the voltage to the segments > >> depending on how many are lit to increase battery life via PWM, but that > >> may not be possible if the boost's enable pin can't handle being PWMed, > >> so I may have to use a driver of some type. The cost/space advantage of > >> using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not > >> gigantic. > > > >Why not just use transistor arrays? > > I suspect the OP's problem is collapsing the "eBay special"... > persistently ignoring the fact that filament-type bulbs have ~10X > current when cold.That 10x could be reduced with a little resistance. And the lines could be turned on one at a time. NT
Reply by ●July 15, 20162016-07-15
On Friday, 15 July 2016 14:56:28 UTC+1, bitrex wrote:> On 07/15/2016 05:54 AM, piglet wrote: > > On 14/07/2016 21:51, bitrex wrote: > >> On 07/14/2016 04:27 PM, John Larkin wrote: > >>> > >>> Seven cold filaments could pull a lot of current. You could do > >>> software tricks to soften the turn-ons, but the display might look > >>> silly. > >>> > >>> > >> > >> I'm going to give preheating the filaments via PWMing the "shutdown" pin > >> of the boost module a try, though I'll have to check the datasheet to > >> see what the delay from a high level applied to that pin to output power > >> good is. > >> > >> If that's not plausible I can try PWMing the "ripple blanking" input to > >> the '47. > > > > Could be easier just to add resistors across LS47 outputs to preheat, > > depending on ease of changing hardware vs software I suppose. > > > > piglet > > > > I'm hoping to get a few PCBs of the circuit I'm working on made if it > turns out alright, so I'd like to keep everything as compact as possible > and do it in software if I can, rather than add a resistor network to > the board. > > In the final design I'd like to ditch the LS chip entirely and simply > use a uP of the same architecture with enough pins to handle all the > segments directly. Many AVR chips are rated to sink 200mA to ground > total through all pins, which surprised me a bit...though this circuit > would push that limit and perhaps make me feel a little uncomfortable. > > I'd also like to dynamically adjust the voltage to the segments > depending on how many are lit to increase battery life via PWM, but that > may not be possible if the boost's enable pin can't handle being PWMed, > so I may have to use a driver of some type. The cost/space advantage of > using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not > gigantic.If PWM isn't an option there are other ways to reduce display current - though not greatly of course. Eg 2 output pins driving one filament, one via a resistor, or even a slightly adjustable voltage supply. Or an LDR/photodiode could adjust brightness according to ambient light etc. NT
Reply by ●July 15, 20162016-07-15
On Friday, July 15, 2016 at 11:35:16 AM UTC-4, John Larkin wrote:> On Fri, 15 Jul 2016 09:56:19 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > > >On 07/15/2016 05:54 AM, piglet wrote: > >> On 14/07/2016 21:51, bitrex wrote: > >>> On 07/14/2016 04:27 PM, John Larkin wrote: > >>>> > >>>> Seven cold filaments could pull a lot of current. You could do > >>>> software tricks to soften the turn-ons, but the display might look > >>>> silly. > >>>> > >>>> > >>> > >>> I'm going to give preheating the filaments via PWMing the "shutdown" pin > >>> of the boost module a try, though I'll have to check the datasheet to > >>> see what the delay from a high level applied to that pin to output power > >>> good is. > >>> > >>> If that's not plausible I can try PWMing the "ripple blanking" input to > >>> the '47. > >> > >> Could be easier just to add resistors across LS47 outputs to preheat, > >> depending on ease of changing hardware vs software I suppose. > >> > >> piglet > >> > > > >I'm hoping to get a few PCBs of the circuit I'm working on made if it > >turns out alright, so I'd like to keep everything as compact as possible > >and do it in software if I can, rather than add a resistor network to > >the board. > > > >In the final design I'd like to ditch the LS chip entirely and simply > >use a uP of the same architecture with enough pins to handle all the > >segments directly. Many AVR chips are rated to sink 200mA to ground > >total through all pins, which surprised me a bit...though this circuit > >would push that limit and perhaps make me feel a little uncomfortable. > > > >I'd also like to dynamically adjust the voltage to the segments > >depending on how many are lit to increase battery life via PWM, but that > >may not be possible if the boost's enable pin can't handle being PWMed, > >so I may have to use a driver of some type. The cost/space advantage of > >using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not > >gigantic. > > Well, you could fast-forward 40 years or so and use LED displays.If his ebay special is one of those Canton Power jobs then it's not half bad. It should be using an all-in-one IC with UVLO, OVP, OCP, OTP, a bunch of other P's, soft-start, and external /EN. Goes to show you really can't make stuff idiot proof. My reading of the problem is adverse interaction with the LiPO or bench PS and the turn-on surge. It should be fixable with 1000uF/ millisecond turn-on required at the input of the boost- to keep it above the 2.5V minimum. Power supplies just don't "fall over" for no reason.> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Reply by ●July 15, 20162016-07-15
On Fri, 15 Jul 2016 10:50:29 -0700 (PDT), tabbypurr@gmail.com wrote:>On Friday, 15 July 2016 17:30:43 UTC+1, Jim Thompson wrote: >> On Fri, 15 Jul 2016 10:50:21 -0500, Tim Wescott <tim@seemywebsite.com> >> wrote: >> >On Fri, 15 Jul 2016 09:56:19 -0400, bitrex wrote: >> >> On 07/15/2016 05:54 AM, piglet wrote: >> >>> On 14/07/2016 21:51, bitrex wrote: >> >>>> On 07/14/2016 04:27 PM, John Larkin wrote: >> >>>>> >> >>>>> Seven cold filaments could pull a lot of current. You could do >> >>>>> software tricks to soften the turn-ons, but the display might look >> >>>>> silly. >> >>>>> >> >>>>> >> >>>>> >> >>>> I'm going to give preheating the filaments via PWMing the "shutdown" >> >>>> pin of the boost module a try, though I'll have to check the datasheet >> >>>> to see what the delay from a high level applied to that pin to output >> >>>> power good is. >> >>>> >> >>>> If that's not plausible I can try PWMing the "ripple blanking" input >> >>>> to the '47. >> >>> >> >>> Could be easier just to add resistors across LS47 outputs to preheat, >> >>> depending on ease of changing hardware vs software I suppose. >> >>> >> >>> piglet >> >>> >> >>> >> >> I'm hoping to get a few PCBs of the circuit I'm working on made if it >> >> turns out alright, so I'd like to keep everything as compact as possible >> >> and do it in software if I can, rather than add a resistor network to >> >> the board. >> >> >> >> In the final design I'd like to ditch the LS chip entirely and simply >> >> use a uP of the same architecture with enough pins to handle all the >> >> segments directly. Many AVR chips are rated to sink 200mA to ground >> >> total through all pins, which surprised me a bit...though this circuit >> >> would push that limit and perhaps make me feel a little uncomfortable. >> >> >> >> I'd also like to dynamically adjust the voltage to the segments >> >> depending on how many are lit to increase battery life via PWM, but that >> >> may not be possible if the boost's enable pin can't handle being PWMed, >> >> so I may have to use a driver of some type. The cost/space advantage of >> >> using one 20 pin SOIC uC vs an 8 pin SOIC uC and a 16 pin SOIC is not >> >> gigantic. >> > >> >Why not just use transistor arrays? >> >> I suspect the OP's problem is collapsing the "eBay special"... >> persistently ignoring the fact that filament-type bulbs have ~10X >> current when cold. > >That 10x could be reduced with a little resistance. And the lines could be turned on one at a time. > > >NTI haven't seen a spec for the "eBay special". I wonder if the OP bothered to observe the "eBay special" output during power-up? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
