Rhinochugger
Retired Oik
OOooh, that Google resistor hart is a bit too complex for me :thinking::thinking::thinking:
Gizzy said:Colour bands = Gold - then brown, purple, yellow
I make that resistor to be 470 ohms, which seems rather low, from the colour bands, yellow, purple, brown. You could check it if you have a multimeter.
ge_rik said:Neil Robinson said:A separate circuit is probably the best way to go. Rather than a second switch I be tempted to use one four pole On Off On switch.
http://www.rapidonline.com/Electronic-Components/4PDT-On-off-on-Min-Toggle-Switch-75-0094 < Link To http://www.rapidonline.co...-Toggle-Switch-75-0094
Good idea, thanks Neil. Fits my philosophy - Keep it Simple
I found one at Maplin which is cheaperPhilbahn said:Something like this David http://compare.ebay.co.uk/like/280490318232?var=lv<yp=AllFixedPriceItemTypes&var=sbar
Not centre-off, according to the Customer Questionsge_rik said:
ntpntpntp said:Not centre-off, according to the Customer Questionsge_rik said:
Rik's circuit shows an on/off switch on the output from the battery so the centre off function isn't really needed on the output to the motor or lighting circuit.ge_rik said:ntpntpntp said:Not centre-off, according to the Customer Questionsge_rik said:
Well spotted !!
R
Neil Robinson said:Rik's circuit shows an on/off switch on the output from the battery so the centre off function isn't really needed on the output to the motor or lighting circuit.
gregh said:First off, do you realise you don?t need a 4 pole switch for the ?second? solution for the lights? A 3 pole one will work.
gregh said:1. do both leds actually light at the same time? I mean once you?ve selected one direction, do the leds at the front and back both light? Does the ?rear? one light at low voltage and then it goes out and the ?front? one comes on at higher voltages?
gregh said:2. Are you sure you?ve wired it as per your diagram in your 1st post. I can see how you would get your described effect if one of those leads from the motor to leds, actually connected to negative.
gregh said:3. have you actually measured the voltage you get across the motor at max output?
gregh said:But concerning your other correspondent?s (Lyndon) long post. I really can?t see how the dimmer can be a ?constant current? output. If it is, what constant current does it put out? The unit says it?s rated at 8 amps, but it can?t be putting that out to your motor.
I had thought of the possibility of the back emf actually driving the leds too, and that lead me to question 1 above. Because while the pulse is ON to the motor, one of the leds will light and when the pulse turns off, the back emf MAY drive current though the OTHER led.
That's a good enough way to explain it. Just remember your multimeter cannot respond to these pulses - it just measures the average voltage. That's why you see a gradual increase as you increase the output.ge_rik said:When I first wired up the unit to the motor and got a slightly erratic performance, I put a multimeter across the output and it gave a smooth rise in (apparent) voltage. I'm assuming Lyndon's response is something to do with the PWM. This is where my theoretical knowledge gets a bit shaky. With PWM, would the peak voltage remain constant but at lower settings the gaps between the peaks be more spread out - then the gaps close as the settings increase? That was my interpretation (but then as I say my knowledge is a bit thin here).
NEVER use the 1st circuit with 2 leds directly in parallel.ge_rik said:PS -Can I just check with you - would the resistance be doubled if I used one ballast resistor when the LEDs are wired in parallel v in series. I've already soldered individual resistors in parallel as per the last diagram - but would like to know for future reference.
ie
|-----------|>|-------------|
-------////------| |-----------------
940R |-----------|>|-------------|
-------////-------|>|-----|>|--------------------------------
600R
v
470R
|------////------|>|-------------|
---------------------| |-----------------
|-----////-------|>|-------------|
470R
ge_rik said:OK. Latest update on this. The 4pole switch arrived today and so I've done some rewiring.
Before wiring in the new switch, I restored the wiring to its former state - but this time added in the other pair of LEDs. As Greg predicted, one set got brighter as the other set got dimmer. When I reversed the switch, the same again, only the other way around. Furthermore, the dimmer unit struggles to reach full power - it does so very slowly - much more slowly than when no LEDs are connected. I tried putting more load on the motor, as Lyndon suggested, but this made no difference.
I still don't know what the underlying problem with the dimmer is. I guess it just wasn't designed to operate motors. One guess is that the frequency is too high for the motor inductance.ge_rik said:Finally, I took the motor out of the circuit completely and just used the unit to power the LEDs. This time they worked as expected - ie reversing switch set forward and only the front lights come on (low at first and then more brightly) - reverse the switch and only the rear lights come on. So, it is something to do with the motor - and maybe something to do with back-emf - which is what Greg hypothesised and I think underpins Lyndon's explanation.
Good luck. Ask if you've got any more questions.ge_rik said:So, I've gone for the easy option. I'm using two of the 4 poles of the switch for the motor and one pole for the lights - as per Greg's suggestion.
Thanks one and all for your thoughts and suggestions. If anyone comes up with another theory I'd be interested. In the meantime I've ordered a book on electronic theory to brush up on my background knowledge.
Rik
gregh said:OK, so maybe I do understand something at least. When I get a chance to sketch some circuits out today, I'll try to explain what's happening with the leds...
Good luck. Ask if you've got any more questions.
ge_rik said:Thanks Greggregh said:OK, so maybe I do understand something at least. When I get a chance to sketch some circuits out today, I'll try to explain what's happening with the leds...
Good luck. Ask if you've got any more questions.
Any info to fill the gaps in my knowledge will be gratefully received. In the meantime - I think I've reached a solution which does the job so I'm a happy tho slightly puzzled bunny.
Rik