Search found 20 matches

by Einar M
Sat Mar 05, 2011 11:01 pm
Forum: General Discussion
Topic: low fuel alert
Replies: 26
Views: 3483

Re: low fuel alert

It seems most likely that the sensor voltage will change from a low amount (1V?) at full to a higher reading at empty, but you will need to measure it to be sure. I can easily make a circuit that latches a led or buzzer on above a set voltage or have them flash or beep once, or flash or beep repeate...
by Einar M
Wed Mar 02, 2011 12:33 am
Forum: General Discussion
Topic: low fuel alert
Replies: 26
Views: 3483

Re: low fuel alert

What I would do is measure the voltage on the 'sender' wire as the tank goes from full to empty (or vice-versa). Let us know what you measure and then we can suggest more. Most likely a comparator swicthing an oscillator or buzzer will work but we need more data.
by Einar M
Wed Feb 09, 2011 9:44 pm
Forum: General Discussion
Topic: TL750M08 - regulated power circuit...HELP
Replies: 24
Views: 2933

Re: TL750M08 - regulated power circuit...HELP

One further point; you should check the specs on the arduinlo. This type of board is rarely designed for high temps; it's not likely to last long.
by Einar M
Wed Feb 09, 2011 9:24 pm
Forum: General Discussion
Topic: TL750M08 - regulated power circuit...HELP
Replies: 24
Views: 2933

Re: TL750M08 - regulated power circuit...HELP

For enclosed spaces reducing total power is desirable. I would recomend a high efficiency 5V switcher and bypass the on board reg. As for Al caps, higher voltage usually means better performance: lower ESR and leakage. Your situation calls for the high temp versions.
by Einar M
Wed Feb 09, 2011 7:56 pm
Forum: General Discussion
Topic: Upping LM781 Output Voltage
Replies: 3
Views: 852

Re: Upping LM781 Output Voltage

Steve's suggestion is the right way. Connecting a resistor from out to 'gnd' pin swamps out the variation in Iq that occurs between units and with varying loads. 10 to 20 mA is recomended, so 1K from out to 'gnd' and 200 ohm from there to gircuit gnd would give 18V out.
by Einar M
Wed Feb 09, 2011 7:27 pm
Forum: General Discussion
Topic: Motor Reverser
Replies: 15
Views: 2310

Re: Motor Reverser

They are for both reverse and over voltage clamping. Make them 3 to 5 volts above V+. I used the circuit with some low volt low current motors ( 3V 20mA ) and the 1K resistors in the base leads provided enough clamping but this won't be enough for higher currents so I drew in the zeners.
by Einar M
Mon Feb 07, 2011 8:18 pm
Forum: General Discussion
Topic: Motor Reverser
Replies: 15
Views: 2310

Re: Motor Reverser

I have drawn up the circuit I described earlier. The circuit Steve gives is the standard but is not a good choice for the DIY ; it self destructs if both inputs go high. I have included a cicuit that does not do this as well. Go to Photobucket.com enter Einarscircuits and look for motor drivers.
by Einar M
Thu Feb 03, 2011 8:20 pm
Forum: General Discussion
Topic: Motor Reverser
Replies: 15
Views: 2310

Re: Motor Reverser

Hi jwax. Either IC is worth having on hand, but all your situation needs is two transistors. Connect emittor/sources to ground and the collector/drains to one side of the motor each and the bases/gates to the other side of the motor through a suitable resistor. Now, when V+ is applied to one side th...
by Einar M
Sat Jan 29, 2011 12:27 am
Forum: General Discussion
Topic: Wireless Headphones 1957
Replies: 18
Views: 2716

Re: Wireless Headphones 1957

I remember doing this back around 1968. I strung a very thin wire ( 36-40 Ga ) once around the room. The pickup coil was a couple hundred turns on a few metal plates from a medium sized audio transformer which I connected to a tape amp like Dean. It's been a while, but I recall it as working very we...
by Einar M
Tue Jan 11, 2011 3:30 pm
Forum: General Discussion
Topic: AC Power Pack for Cordless Power Tools
Replies: 26
Views: 4441

Re: AC Power Pack for Cordless Power Tools

For 2400 mAH batteries typical self discharge rates are 1 mA for NiCd and 100 uA for NiMH. Rather than a timer setup it would be easier to supply this current thru a resistor, posssibly putting a LED in series so you can see whats going on. If the LED is too dim then add a PNP trans this way: connec...
by Einar M
Tue Jan 11, 2011 3:15 pm
Forum: General Discussion
Topic: Question about relays..
Replies: 9
Views: 1556

Re: Question about relays..

I know zero about MC, but would assume it uses phase control to vary the lamp brightness. This envolves turning on the SSRs at a different point in each half cycle; 120 times a second. Mech relays cannot handle this, no matter what you try. The only solution is SSRs. Probably you could drive them fr...
by Einar M
Sun Jan 02, 2011 3:11 pm
Forum: General Discussion
Topic: 1,000 LED Sequencer
Replies: 45
Views: 8260

Re: 1,000 LED Sequencer

Good to hear back from you. Your idea was inventive and should get the prize for fewest ICs. Often the simplest circuit invovles finding the right ICs. There is nothing creative in my suggestion. The '4514 is a 4 to 16 decoder with active high outputs and drives LED anodes and the '4515 is the same ...
by Einar M
Wed Dec 29, 2010 4:34 pm
Forum: General Discussion
Topic: 1,000 LED Sequencer
Replies: 45
Views: 8260

Re: 1,000 LED Sequencer

This thread may no longer be active but has lots of good ideas. My suggestion would be some 4514 and 4515 chips. Have one drive the horz. lines and the other the vert. Add 16 Rs and some counters or whatever And you have a big matrix thats fairly easy to wire up. (get the HC parts for 20 mA at 5V.)
by Einar M
Wed Dec 29, 2010 3:06 pm
Forum: General Discussion
Topic: battery voltage monitor - help
Replies: 23
Views: 3864

Re: battery voltage monitor - help

I would like to fix the link given above, but can't find the edit function. Some explanation of the circuits posted: the grn to red blend is acheived by making an osc sweep thro the voltage range desired. This is normally about 100Hz and appears solid; to create a visible flash the freq is reduced t...